Yes, the Jackson manual parser design is quite different from other libraries. In particular, you will notice that JsonNode has most of the functions that you would typically associate with array nodes from other APIs. As such, you do not need to cast to an ArrayNode to use. Here's an example:
JSON:
{
"objects" : ["One", "Two", "Three"]
}
Code:
final String json = "{\"objects\" : [\"One\", \"Two\", \"Three\"]}";
final JsonNode arrNode = new ObjectMapper().readTree(json).get("objects");
if (arrNode.isArray()) {
for (final JsonNode objNode : arrNode) {
System.out.println(objNode);
}
}
Output:
"One"
"Two"
"Three"
Note the use of isArray to verify that the node is actually an array before iterating. The check is not necessary if you are absolutely confident in your data structure, but it's available should you need it (and this is no different from most other JSON libraries).
Yes, the Jackson manual parser design is quite different from other libraries. In particular, you will notice that JsonNode has most of the functions that you would typically associate with array nodes from other APIs. As such, you do not need to cast to an ArrayNode to use. Here's an example:
JSON:
{
"objects" : ["One", "Two", "Three"]
}
Code:
final String json = "{\"objects\" : [\"One\", \"Two\", \"Three\"]}";
final JsonNode arrNode = new ObjectMapper().readTree(json).get("objects");
if (arrNode.isArray()) {
for (final JsonNode objNode : arrNode) {
System.out.println(objNode);
}
}
Output:
"One"
"Two"
"Three"
Note the use of isArray to verify that the node is actually an array before iterating. The check is not necessary if you are absolutely confident in your data structure, but it's available should you need it (and this is no different from most other JSON libraries).
In Java 8 you can do it like this:
import java.util.*;
import java.util.stream.*;
List<JsonNode> datasets = StreamSupport
.stream(obj.get("datasets").spliterator(), false)
.collect(Collectors.toList())
As you said its an Array. Cast the node to an ArrayNode. Select the first element [0] and call the getter. Should be it. Or check out this: https://stackoverflow.com/a/16793133/15565539
Instead of 4 lines you can just type
String s = rootnodeResolution.iterator().next().path("id").asText();
Moving my comment to an answer, as it got upvoted a lot.
This should do what the OP needed:
new ObjectMapper().convertValue(jsonNode, ArrayList.class)
A quick way to do this using the tree-model... convert the JSON string into a tree of JsonNode's:
ObjectMapper mapper = new ObjectMapper();
JsonNode rootNode = mapper.readTree("...<JSON string>...");
Then extract the child nodes and convert them into lists:
List<Double> x = mapper.convertValue(rootNode.get("x"), ArrayList.class);
List<Double> y = mapper.convertValue(rootNode.get("y"), ArrayList.class);
A slight longer, but arguable better way to do this is to define a class representing the JSON structure you expect:
public class Request {
List<Double> x;
List<Double> y;
}
Then deserialized directly as follows:
Request request = mapper.readValue("...<JSON string>...", Request.class);